1. Field of the Invention
The present invention relates to a headlamp for a motor vehicle of the type in which a reflector within a lamp body is provided with a bubble tube type level vial for detecting a vertical inclination of the reflector.
2. Related Art
A conventional headlamp of this type is disclosed, for example, in Unexamined Japanese Patent Publication (OPI) No. Hei. 4-198830 as illustrated in FIG. 5. As shown, the headlamp includes a lamp body 1 and a front lens 2 for defining a lamp chamber S with the lamp body 1. The lamp chamber S accommodates therein a reflector 3 mounting thereon a bulb 4 acting as a light source is supported by an aiming mechanism 5 so that the reflector is tiltable with respect to the lamp body 1. A bubble tube type level vial 6 is disposed on the reflector 3. A degree of vertical inclination of the reflector 3 (an angle of vertical inclination of a light axis L of the headlamp) is detected by the level vial 6. That is, the level vial 6 indicates the angle of vertical inclination of the reflector 3. Reference numeral 7 designates an inclination detector 7 for detecting an angle of horizontal inclination (an angle of horizontal inclination of the light axis L of the headlamp) of the reflector 3, which is disposed between the aiming screws composed of the aiming mechanism 5 and the rear wall of the lamp body 1.
In the conventional headlamp thus structured, the level vial 6 is disposed on the upper wall of the reflector 3. Because of this structure, heat generated by the bulb 4 is easily transferred to the bubble tube of the level vial 6 through the reflector 3. For this reason, a bubble housed within the bubble tube may be shifted from a zero point thereof due to the generated heat, thereby indicating an improper angle of vertical inclination of the reflector.
On the other hand, Unexamined Japanese Patent Publication (OPI) No. Hei. 3-91604 shown in FIG. 6 discloses an approach to minimize the influence of the heat from the bulb 4 toward the bubble in the bubble tube in a manner that the level vial 6 is disposed on the rear side of the reflector 3 in a separated fashion. This approach succeeds in reducing the influence of the heat on the bubble of the bubble tube to some extent, however, its thermal isolation capability is still insufficient. The influence of the heat may be further reduced by further separating the level vial 6 from the rear side of the reflector 3. This approach creates another problem of increasing the size of the lamp body, however.